Basic refractory



United States Patent 3,310,414 BASIC REFRACTORY Allen M. Alper, Coming,and Robert N. McNally, Horseheads, N.Y., assignors to CorhartRefractories Company, Louisville, Ky., a corporation of Delaware NoDrawing. Filed Feb. 8, 1965, Ser. No. 431,168 5 Claims. (Cl. 106-58)This invention relates to a novel fused basic refractory material andparticularly such refractory material that is especially suitable foruse in basic oxygen steelmaking vessels. As is well known, fusedrefractory is the type of refractory material which is'commonly producedby melting a mass of refractory material of the desired composition andthen cooling the molten refactory material to form a solidifiedrefractory mass. The molten refractory material may be cast andsolidified in a mold to form bodies of particular shapes, or the moltenrefractory can be solidified within the same container in which it wasmelted (i.e. solidified in situ). Such solidified monolithic bodies orproducts are commonly denoted as fused cast refractory. Additionally,the novel fused basic refractory material can be made in the form ofsmall granules or grain by well known techniques of disintegrating themolten refractory into small globules or particles that are thensolidified, or by crushing larger solidified monolithic masses of therefractory.

The environmnet in basic oxygen steelmaking vessels presents a rathersevere corrosion and erosion problem for the Working linings of thevessels, particularly for the side wall linings. The more detrimentalfactors of such environment contributing to this problem are: the hightemperatures developed by the oxygen blast, the violent action of thesteel-forming contents in washing and abrading against the workinglinings, the corrosive nature of the high lime-to-silica ratioferruginous slags and slag vapors, and the reducing nature of the carbonmonoxide atmosphere developed. Refractories that have been commerciallyutilized for working linings heretofore in these furnaces have beenmainly those of burnt or tar bonded dolomites and magnesites or mixturesthereof, or of fused mixtures of magnesites and chrome ores. Althoughthese refractories exhibit a relatively modest corrosion-erosionresistance in basic oxygen vessel environments, there has been a greatdesire upon the part 'of the operators of these vessels for a refractorymaterial having a greatly improved corrosion-erosion resistance in orderto increase the life of the working linings, which life has commonlybeen relatively short with the prior commercial rerfactory materials.

We have now discovered a novel basic fused refractory material thatpossesses a corrosion-erosion resistance in basic oxygen vesselenvironments greatly superior to that of the common commercialrefractory materials used heretofore. Accordingly, it is an object ofthis invention to provide such novel and improved basic fused refractorymaterial. It is another object of this invention to provide a novel andimproved basic fused refractory material capable of longer service lifeas a basic oxygen vessel .working lining than has been attainable withthe common commercial refractory materials used heretofore. Otherobjects and advantages of the present invention will become aparent fromthe detailed description below.

Our novel basic fused refractory material is essentially characterizedby a composition of, analytically in percent by weight, 60 to 95% MgOand 5 to 40% MnO However,,for some uses, the MnO content can be as lowas 1% with a corresponding MgO content as high as 99% where greaterdifiiculty and expense in manufacturing and substantially lower hotstrength (based on modulus of rupture in flexure at elevatedtemperatures) is not objectionable. Although the composition can be com-3,3 10,4 14 Patented Mar. 21, 1967 ice posed wholly of the two oxideconstituents as described above, the composition may beneficiallyinclude limited amounts of other oxides (as diluents, impurities oradditives) forming a total remainder content of not more than 35% ofoxide selected from one or more of the following three groups of oxides.The first group consists of FeO, CaO, Cr O and mixtures thereof in atotal amount of up to 30%. The second group consists of TiO ZrO andmixtures thereof in a total amount being less than 20%. The third groupconsists of BaO, SrO, A1 0 B 0 SiO P 0 rare earth oxide and mixturesthereof in a desired total amount being less than 3% to assure good hotstrength, although the latter total amount can be somewhat higher butless than 10% where lower hot strength is not objectionable in basicoxygen furnace service or in other applications, such as checkers forglass or metallurgical furnaces. The permissable inclusion of thelimited amounts of other oxides permits the use of cheaper, less pureraw materials and contributes to greater ease of melting withoutdestroying the properties making the objects of this invention possible.Furthermore, some of these added constituents provide additional specialbenefits as will be more fully described below.

A particularly desirable composition of the basic fused refractorymaterial according to this invention consists of to MgO, 5 to 25% MnOand a remainder of other oxide totalling not more than 25% selected fromone or more of the following groups: 1) up to 20% (and desirably atleast 1%) of FeO, CaO, Cr O and mixtures thereof, (2) less than 15% (butdesirably at least 1%) of TiO;, ZrO and mixtures thereof, (3) less thanof R210, SrO, B203,- Slog, P205, rare earth oxide and mixtures thereof.

This refractory material is essentially or substantially a monophase, orsingle phase, crystalline structure of the periclase type of latticewith manganese in solid solution therein and can be represented by theformula:

Sometimes a minor amount (usually less than 5% by weight) of a spinelphase is formed by the oxides of magnesium and manganese, which isbelieved to be MgO-Mn O or (Mg,Mn)O-Mn O Of course, when the notedadditional constituents other than MgO and MnO are included, these alsomay provide a minor amount of spinel and/ or other crystalline phase,although such additional constituents may also be largely in solidsolution in the periclase lattice. The crystals interlock as is typicalof fused type refractory material. There are no substantial amounts oflower-melting, intergranular, eutectic phases that allow the material tobe rapidly corroded or penetrated by slag or slag vapors.

This superior corrosion-erosion resistant basic fused refractorymaterial is readily manufactu rable into substantially crack-free bodiesby melting a mixtureof suitable raw materials, for example, calcinedmagnesite and manganese oxide ore. As will be appreciated, relativelyhigh temperatures (e.g. approx. 20002800 C.) are required to fuse andcompletely melt the compositions of this invention. Preferably,conventional electric arc. melting furnaces utilizing graphiteelectrodes are employed, although any other suitable means can be usedas desired. The raw batch materials are suitably proportioned to providethe desired final composition and, preferably, are premixed ingranulated form prior to charging into the melting furnace.

The more usual form of our novel refractory for lining basic oxygenvessels is that of bricks cast to shape, orcut from billets that arecast, by pouring the molten batch material into conventional preformedmolds of any suitable material, e.g. graphite, bonded sand, or steel,and allowing it to cool and solidify according to conventional practice,for example, as disclosed in United States Patent 1,615,750 to G. S.Fulcher, to which reference may be 4 ples, of the invention and of priormaterials, and their properties or characteristics. 1 Table I showsbatch mixtures (in percent by weight) that were electric arc melted andthe chemical composihad. If desired, the novel refractory material canbe tions of the solidified blocks as calculated from the analymelted andsolidified in the same container. However, if ses of the oxides enteringinto the batch mixtures. All desired, a stream of the molten refractorycan be disinthe examples in Table I are of fused refractory materialtegrated by known conventional techniques into small of this invention.globules or particles of desired size and solidified as a The variousconstituents in the batch mixtures of Table mass of fused granularmaterial. This granular material, I were provided by common commerciallyavailable raw with or without other additional refractory material, canmaterials whose typical chemical analyses, in weight perthen be used toform rebonded bricks of special shape cent, were as follows: that arenot as easily formed by directly casting the shape Calcined magnesite.98.51% MgO, 0.86% CaO, from the molten material. Moreover, the granularma- 0.28% SiO 0.22% Fe O 0.13% ignition loss. terial for making rebondedbricks can be obtained by M110 Concentrate. 79+% MnO 5.25% A1 0 crushingblocks, billets or boules of the novel refractory 2.75% Fe, 1.85% SiOmaterial. M710 Ore. 62.0% MnO 18.0% Fe O 7.05%

As previously noted, our novel fused refractory may SiO 3.03% A1 0 0.55%P 0 consist solely of the oxides of magnesium and manganese Magnetite.98.5 Fe O 0.77% S10 0.24% in the ranges specified above. However, it ispreferred A1 0 0.20% TiO 0.08% MgO, 0.02% Mn.

TABLE 1 Example N0 1 2 3 4 5 6 7 8 9 10 11 Calcined Magnesite, percent95 95 85 85 75 70 80 8O 7O 70 80 M1102 Concentrate, percent 5 15 MnOzOre, percent 15 10 15 15 15 10 Magnetite, percent 10 5 15 Calcined Lime,percent. 15 Rutile, percent 10 MgO, percent 93.7 93.7 83.8 83.8 74.069.1 78.9 78.9 69.1 69.2 78.9 02, percent 4.4 3.4 13.3 10.3 22.2 20.56.8 10.3 10.3 10.3 6.8 FeO, percent. 0. 4 1.2 0. 7 3. 2 0.9 6.1 12.0 8.117.9 3. 1 2.3 05.0, percent 0.8 0.8 0.7 0.7 0.7 0.6 0.7 0.7 0.6 15.1 0.7SiO percent- 0. 4 0. 7 0. 6 1. 4 0. 7 2. 5 1.1 1. 4 1. 5 1. 6 1. 0A1203, percent 0.3 0.2 0.9 0.5 1. 5 1.0 0.4 0.5 0. 5 0.6 0. 4 P205,percent 0. 1 0.2 0. 1 0.1 0.1 0. 1 0.1 T102, percent 9.8 Percent SlagCut i 21 17 26 19 21 23 34 14 Avg. Modulus of Rupture a 1,340 C. .s.i.)330 130 1, 345 1,780 1,330 1,209 720 2,020 2,450 2,250

to use less pure, less expensive commercial raw materials Calcinedtime.95.65% CaO, 1.30% S10 0.85% that may additionally provide one ormore of the other MgO, 0.85% R 0 0.04% S, 0.85% ignition loss.

specified oxides (e.g. FeO, CaO, A1 0 SiO etc.) Within the limitsspecified above. These limited amounts of additional oxides do notdeleteriously affect the essential characteristics of our novelrefractory and, in some cases, they enhance these characteristics orprovide additional special benefits. For example, A1 0 B 0 SiO; and/ orP 0 tend to increase hydration resistance and facilitate melting, Cr Oand ZrO tend to increase resistance to hot siliceous slags and vapors,and TiO tends to increase hot strength.

Particularly good properties and results for basic oxygen vessel servicewere noted for four more specific preferred composition areas. The firstarea consists of 70 to 95% MgO, 5 to 25% MnO less than 5% FeO, less than2% CaO, less than 2% SiO less than 2% A1 0 less than 0.5% P 0 and thesum of SiO +Al O +P O being less than 3%. The second area consists of 65to 90% MgO, 5 to 20% MnO 5 to 20% FeO, less than 2% CaO, less than 2%SiO less than 1% Al O less than 0.5 P 0 and the sum of SiO +Al O +P Obeing less than 3%. The third area consists of 65 to 90% MgO, 5 to 20%MnO not more than 20% of FeO+CaO, the CaO being at least 5% and the FeObeing less than 5%, less than 2% SiO less than 1% A1 0 less than 0.5 P 0and the sum of SiO +Al O +P O being less than 3%. The fourth areaconsists of 70 to 95% MgO, 3 to 20% MnO 2 up to but less than 15% T10less than 5% FeO+CaO, the 0210 being less than 2%, less than 2% S10 lessthan 1% A1 0 less than 0.5% P 0 and the sum of SiO +Al O +P O being lessthan 3%. The first, second and fourth areas appear to provide bettercorrosion-erosion resistance than the third area.

By way of illustrating and providing a better appreciation of thepresent invention, the followingdetailed description and data are givenconcerning refractory sam- RutiIe.-9698% TiO 1% max. Fe O 0.3% ZrO 0.3%A1 0 0.25% SiO 0.1% Cr O 0.29% V 0 0.025-0.05% P 0 0.01% S.

The present slag cut data shows the resistance to high lime-to-silicaratio ferruginous slag by the various samples and is based upon the testcomprising placing 1 /2" x 1 x /2 samples in a furnace having a COatmosphere adapted to approximate a basic oxygen vessel environment. At1700 C. for about 2 /2 to 3 hours, the samples were passed, with one oftheir largest surfaces facing upward, through a downwardly directedstream of molten basic slag droplets at a substantially uniform rate of60 times per hour until 2 kilograms of slag had been employed. The slagwas representative of basic oxygen furnace slag developed during theproduction of a heat of steel and had the following composition, byweight: 23.75% Fe O 25.94% SiO 40.86% CaO, 6.25% MgO and 3.20% A1 0 Atthe end of the test, the average thickness of the samples was measuredand compared with the original /2" thickness prior to testing. Theresults are expressed as a percentage change in thickness (calledpercent slag cut).

In contrast to the present invention, two samples of more conventionaltar bonded dolomite brick both exhibit ed a slag cut of 100% (i.e. thesesamples were completely cut in half) in the same test. Sample of commoncommercial basic fused refractory made from a mixture of essentially 55%by weight magnesite and 45% by weight Transvaal chrome ore(representative of the material according to US. Patent 2,599,566)exhibited slag cuts of 40100% in the same test.

While the hereindescribed novel basic fused refractory material isespecially suitable for basic oxygen vessel linings, it will be apparentthat this material can be employed in other forms, structures and usesas desired or deemed 5 suitable without departing from the scope of thisinvention.

As used in this specification, (1) all the percentage quantities of thespecified oxides are expressed analytically in percent by Weight, andthey include all of the respective metal or metalloid contents asanalyzed and then calculated in terms of the specified oxides, althoughsome of the metals and/ or metalloids may not exist in the material inthe precise form or oxidation state of such oxides (for example, someiron oxide may exist as Fe O or Fe O although much of it is usuallypresent as FeO due to the reducing nature of the melting environmentemployed), and (2) rare earth oxide means the common oxide of one ormore of yttrium and the lanthanide series elements having an atomicnumber of 57 to 71.

We claim:

1. A fused refractory material having interlocking crystals andconsisting of, analytically by Weight, 65 to 90% MgO, 5 to 20% MnO 5 to20% FeO, less than 2% CaO, less than 2% SiO less than 1% A1 less than0.5% P 0 and the sum of SiO +Al 0 +P O being less than 3%.

2. A fused refractory material having interlocking crystals andconsisting of, analytically by weight, 70 to 95% MgO, 3 to 20% MnO 2 upto but less than TiO less than 5% FeO-l-CaO, the CaO being less than 2%,less than 2% SiO;, less than 1% A1 0 less than 0.5%

P 0 and the sum of SiO +Al O +P O being less than 3%. 4 3. A fused castrefractory having interlocking crystals and consisting of approximately,analytically by Weight, 79% MgO, 10% MnO 8% FeO, 0.7% CaO, and thebalance 4. A fused cast refractory having interlocking crystals andconsisting of approximately, analytically by weight, 69% MgO, 10% M 18%FeO, 0.6% CaO and the balance SiO2+A1203+P205. V

5. A fused cast refractory having interlocking crystals and consistingof approximately, analytically by weight, 79% MgO, 7% MnO 10% TiO 3%FeO+CaO and the balance SiO2+A1203+P205.

References Cited by the Examiner UNITED STATES PATENTS 4/1938 Sullivan1066O OTHER REFERENCES J. E. POER, Assistant Examiner.

1. A FUSED REFRACTORY MATERIAL HAVING INTERLOCKING CRYSTALS ANDCONSISTING OF, ANALYTICALLY BY WEIGHT, 65 TO 90% MGO, 5 TO 20% MNO2, 5TO 20% FEO, LESS THAN 2% CAO, LESS THAN 2% SIO2, LESS THAN 1% AL2O3,LESS THAN 0.5% P2O5 AND THE SUM OF SIO2+AL2O3+P2O5 BEING LESS THAN 3%.